The present invention relates to a sheet stack finish-processing unit, and more specifically, it relates to such a unit disposed lateral of an image forming apparatus such as a copying machine, for finish-processing sheets discharged from the image forming apparatus. In addition, the present invention relates to an image forming apparatus including the sheet stack finish-processing unit.
A conventional image forming apparatus such as a copying machine may have a sorter for sorting and storing into stacks image-formed sheets. One type of sorter includes a stapler for stapling the stacks of sheets.
Japanese Patent Laying-Open No. 231757/1989 discloses a conventional sorter provided with a stapler. The sorter has a plurality of bins sorting slicers by receiving them into storage in a given order. The bins can be translated vertically; and in the conventional sorter, as the bins are translated, a predetermined spacing is provided above that bin brought adjacent a sheet supplier, through which spacing sheets are transported from the sheet supplier into each bin in turn. A stapler provided in the sheet supplier is pivotal through a predetermined angle, assuming either a drawn position, wherein it will not interfere with passage of the bins, or a stapling position, in which its stapling operation is carried out.
In the above-described sorter, a stapler pivoting mechanism must be provided, complicating the structure. In addition, since the stapling operation can only be performed in the fixed location, the stapling position along the corresponding end of a sheet stack is not variable, nor can the slack be stapled in a plurality of marginal positions. Hence use of the stapling function is singularly restricted.
In addition, the above-described sorter cannot accommodate any number of stacks of stapled sheets greater than the number of bins. Therefore, when a greater number of copies are to be produced, an operator must empty stapled stacks of sheets from the bins in order to allow succeeding sheets to pass thereinto.
Japanese Patent Application Laid-Open No. 165270/1988 discloses a sorter consisting of a sorting portion and a stapling portion. When sheets are to be stapled by the sorter, stacks formed in the sorting portion are transported to the stapling portion, and then a stapler provided in the stapling portion staples the stacked sheets. Accordingly, the sorter can handle a number of copies greater than the number of bins provided in the sorting portion. In the foregoing sorter, however, the stapler is provided under the bins, and a stacking portion into which finish-processed stacks of sheets are stored is disposed under the stapler. Therein, it is difficult for an operator to take out the stacks of sheets. Moreover, before each stack of sheets is stapled, the previously stapled stack of sheets is discharged into the stacking portion, adding to required operating time.